Characteristics of spring barley varieties for organic farming

Modern spring barley varieties have been developed with the aim of combining high productivity and standardised product quality under high-input conditions using pesticides for control of weeds, diseases and insects as well as heavy application of nutrient-rich and water-soluble inorganic fertilizers. In the organic growing system, biotic and abiotic stresses have to be overcome by growing the appropriate varieties and by practicing good farm management. The important spring barley traits to be considered in organic farming are related to the inherited viability and adaptation of plants to survive biotic and abiotic stresses and includes competitive ability (morphology, weed tolerance, growth rate, allelopathy), disease resistance (morphology, specific and non-specific resistance proporties, disease tolerance) and nutrient acquisition ability (root morphology, nutrient uptake and use efficiencies, low-nutrient tolerance, symbioses). An important question is whether modern spring barley varieties possess the right combinations of these characteristics to ensure a stable and acceptable yield of good quality when grown under different organic growing conditions. We know that varieties often perform and yield differently in different environments due to genotype-environment interactions, so it may be important to evaluate characteristics of varieties in organic as well as in conventional farming systems. However, it remains unclear to date whether the differences between the conventional and the organic growing systems are large enough to justify breeding and testing of varieties in both environments. Extensive field experiments and refined statistical methods are needed to clarify this. Characterisation of varieties as part of the official variety testing is at present done under conventional farming conditions in Denmark. The aim of a newly started inter-institutional Danish research project within The Danish Research Center for Organic Farming (DARCOF) with project participants from The Royal Veterinary and Agricultural University, Danish Institute of Agricultural Sciences and Risø National Laboratory is to Identify combinations of plant characteristics required for a barley crop to be successful in organic growing systems and develop methodologies for measuring these characteristics. Evaluate, by investigating genotype-environment interactions, the need for specific variety trials for organic farming, and if necessary implement such trials. Improve yield and yield stability in different organic farming systems by strategic use of the appropriate varieties and variety mixtures. Investigate the potential of different variety mixtures for reducing diseases and weeds and increasing nutrient uptake efficiency. Obtain new knowledge on plant competition, disease complexes, epidemiological models, nutrient acquisition and associations between molecular markers and agronomical traits. The results of the first-year trials on three organic workshop areas and in two conventional fields with about 120 mostly modern varieties and a few variety mixtures will be discussed. The preliminary analyses indicate large variation in yield between the different varieties

Discussion documents – SUSVAR Visions Workshop, Karrebæksminde, Denmark, April 2008

Seven discussion documents were made during the SUSVAR Visions workshop ‘Sustainable cereal production beyond 2020: Visions from the SUSVAR1 network’, Karrebæksminde, Denmark, 14-16 April 2008. At the workshop, one discussion documents was written for each of the topics mentioned below. In total 55 persons from 21 European countries participated in the process. The participants came from different disciplines: genetics, plant breeding, genetic resources, agronomy, plant pathology, soil science, biometry and system analysis, all specialised in the area of cereal production. The approach taken at the workshop was to focus on envisioning the future of sustainable agriculture, especially cereal production. This was done by scientific creative thinking on the basis of possibilities in breeding, management and seed production and not on the basis of traditional problem solving. We followed a strategy commonly used in industrial management based on the premise “imagining the future is shaping the future”. The method “appreciative inquiry” was applied supported by a professional facilitator. Experience shows that this way of working sparks engagement and creativity and that progress and results can be reached within a short time. Focus was on the following topics of relevance to cereal production: - Competition between food and bioenergy, - Soil fertility management, - Economical and legal conditions for variety improvement, - Participation of stakeholders, - Plant breeding strategies, - Food and feed processing improvements, - Sustainable land use. The initial process was to visualise the most desirable future scenario for the seven essential topics in food and agriculture systems. This process was unhindered by no requirement for a market-driven goal. Each topic was discussed in relation to a broader socio-ecological system with a focus on the means to reach the desired and more sustainable outcomes. The next step at the workshop was to produce the discussion documents. The final stage of the process is to connect the topics in a completed vision of cereal production within a future sustainable socio-ecological system. This is in progress by a group of key persons within the network, e.g. the working group leaders (in preparation for publication in a scientific journal)

Opinions on biogas in organic farming

The application of biogas technologies in organic farming involves many considerations: Benefits like improved fertilizer supply and fossil fuel savings are opposed to concerns about economical risks and incompliance with organic principles. A questionnaire developed by Risø DTU gives an idea about some Danish stakeholders’ perceptions of benefits and drawbacks

Biogas i økologisk jordbrug

Hvilke faktorer har størst betydning for udbredelsen af biogasteknologien? Offentlige tilskud er svaret fra en rundspørge

Yield of spring barley mixtures as a function of varietal and environmental characteristics

To design good variety mixtures it is important to understand the influence of varietal and environmental characteristics on mixing effect, e.g. what characteristics are more beneficial when all mixed varieties express it highly and what characteristics are more beneficial when the mixed varieties express it to varying extent. However, as it is generally impossible to manage more than a few experimental combinations in each field trial, information on general relationships and factors of importance for the successful design of variety mixtures may be overlooked. Using meta-regression (e.g. Houwelingen et al. 2002), numerous results of such trials can be combined, and the influence of varietal and environmental factors on mixing effect can be elucidated. Here, two specific hypotheses were investigated: 1. Variation in straw length among component varieties will increase mixing effect due to enhanced potential for resource utilization. 2. Mixing effect will increase with more stressful environments due to increased importance of mechanisms like complementarity and compensation. Meta-analyses with and without covariates were applied to test the hypotheses and elucidate factors of importance for mixing success. The simple meta-analysis showed significant overall increase in yield due to mixing of varieties in spite of slightly opposing results between individual trials. However, the meta-regressions were unable to support the two hypotheses: the mixing effect was not affected by component variation in straw length, and the mixing effect was slightly increasing with environmental yield potential, which was actually arguing against the hypothesis. Further analyses must be done to investigate whether these trends can be found in other data sets and whether further covariates may assist interpretation. The results also show that experimental trials with extraordinarily small experimental variation may influence the conclusions of the analysis. The excluded trial was performed at an experimental farm which is known to provide rather homogenous growing conditions. This information is not readily included in the current use of weighting. In the work to come, we will assess the appropriateness of the current application of inverse variance as weights in meta-analysis of field trial data. Other critical issues that need further investigation include the possible lack of independence between estimates due to shared environments and common component varieties of mixtures

Meta-analysis is a powerful tool to summarize variety mixture effects - exemplified by grain yield and weed suppression of spring barley

In a new project, we aim to increase the general understanding of the power of meta-analysis to combine existing experimental results on variety mixtures. In this way, explanatory power can be increased compared to separate analyses and overall measures and relationships may be revealed. We will thus pursue to uncover a number of critical issues, including the relative importance of various traits and trait combinations on mixing success. To demonstrate the methods of meta-analysis applicable for variety mixture data, we considered a data set consisting of grain yield and weed ground cover assessments in 16 field trials of six 3-component variety mixtures and their components (part of the Danish BAR-OF field trials). The effects of mixing were analysed separately for each field trial and the results used in a meta-analysis in combination with their standard errors. We also analysed the mixing effects of each mixture by fitting a linear model to the entire data set. Both methods showed an overall positive mixing effect on grain yield and a trend for less weed to be found in variety mixtures. Finally, strengths and shortcomings of the methods are highlighted

Effects of inter-varietal diversity, biotic stresses and environmental productivity on grain yield of spring barley variety mixtures

Varietal seed mixtures tend to increase and stabilize crop yields, yet their application is sparse. Large-scale cultivation of variety mixtures may require a better understanding of how inter-varietal interactions and their interaction with the environment may influence the grain yield of variety mixtures relative to their component varieties. For this purpose, six variety mixtures of spring barley and 14 component varieties were grown in each of 17 trial environments. A total of 28 observed and a priori plant characteristics, including grain yield, disease severity and weed competitiveness, were derived for each component variety in each trial. The relationship between inter-varietal diversity of each characteristic and the mixing effect on grain yield was analysed. Additionally, various types of yield stability were estimated and compared among mixtures and component varieties. One mixture out-yielded all of its component varieties in almost half of the trial environments. Inter-varietal diversity in grain yield potential correlated significantly with mixing effect, as did straw length diversity when weighted with weed pressure. The grain yields of most mixtures were more stable across environments than their component varieties when accounting also for the general response to environmental productivity. Hence, most mixtures adapted slightly better to environmental productivity and were less sensitive to environmental stress than their component varieties. We conclude that the efficacy of variety mixtures may be enhanced by mixing relatively high-yielding varieties differing in responsiveness to environmental productivity

Genetic potential for grain yield in spring barley varieties and variety mixtures in variable organic environments

For organic crop production, well-characterised varieties increase the possibilities for controlling diseases and weeds and compensating for deficits in nutrients. Variation in grain yield was studied in about 150 spring barley varieties and variety mixtures and 20 combinations of location, growing system and year. Choice of variety was found to be as important a factor for grain yield as other factors in the management. Some variety mixtures out yielded even the best variety in the mixture, when this was grown in pure stand. Finally, a concept for organic variety testing of spring barley was developed. This Danish project is part of a European COST Network on sustainable low-input cereal production (SUSVAR) which coordinates studies in different countries on variety mixtures, composite crosses and variety testing